1. Field of the Invention
The present invention is concerned with the use of calcitonin gene-related peptides and of the analogues thereof for the treatment of erectile dysfunctions.
2. Description of the Prior Art
Calcitonin gene-related peptides are known and are described, for example, in published European Patent Specification No. 0,212,432 and in U.S. Pat. Nos. 4,530,838 and 4,687,839, but such peptides are described therein as having actions on memory, sensitivity to pain, and lowering of the blood pressure, and or the secretion of gastric juices.
About 5% of men in the 40th year of their life and 20% in the 60th year of their life suffer from an erectile dysfunction. Due to the loss of potency, the bodily, psychological and social self-assurance of men and especially of young men is shaken. Patients with chronic erectile dysfunction are made uncertain in their sexuality and personality and are to be regarded as being ill.
Until the 1970's, potency disturbances were attributed to psychogenic causes, and were thus treated with psychotherapeutic measures as well as testosterone and aphrodisiacs of debatable value. Only after investigation of the physiology of erection was it ascertained that, in the case of more than 60% of the patients, organic causes bring about the disturbance of the erection, in which autonomic efferences from the parasympathetic part of the sacral centre, neurotransmitters, dilation of the penile arteries, relaxation of the cavernosal spaces and constriction of the veins play a part. In more than 70% of the cases, vascular factors originally participated, such as pathological arterial blood supply or abnormally increased venous drainage from the cavernosal spaces. Neurogenic disturbances are involved in about 20% of the cases.
The oral therapy of these organically caused dysfunctions with vasoactive substances, such as yohimbine, phenoxybenzamine, terbutaline, bethanechol, levodopa, verapamil or theophylline proved to be useless. Besides the use of prosthetic implants or of revascularization operations, an intracavernosal injection of papaverine (Virag, Lancet, 2, 938, 1982), of the .alpha.-receptor blocker phenoxybenzamine (Brindley, Br. J. Psychiatr., 143, 332/1983) and of a combination of papaverine and the .alpha.-receptor blocker phentolamine (Stief, Urologe A, 25, 63/1986) proved to be successful. The latter therapeutic method can be carried out by the patients themselves and is referred to as erectile tissue autoinjection therapy.
However, a sometimes undesired prolonged erection with the danger of priapism in the case of the use of papaverine, undesired pain in the case of the use of phenoxybenzamine, as well as the possible cancerogenesis of this compound, proved to be disadvantageous.
In animal experiments (Cynomolgus monkey), in the case of 1-2 intracavernosal injections of papaverine per week over a period of 12 months, extensive fibrous formation in further parts of the erectile tissue were ascertained which, in the case of humans, would lead to extremely negative long-term results since, in the case of a fibrous formation in the corpus cavernosum, an erection can no longer be achieved.
The use of acetylcholine is, in the case of only a brief period of erection, associated with strong systemic side effects and the injection of prostaglandin E.sub.1 is refused by patients because of the intense pain caused by this drug.